为什么上传到 S3 的文件具有内容类型应用程序/八位字节流，除非我将文件命名为.html？

您必须在代码中执行其他操作。我刚刚使用1.9.6 S3 SDK尝试了您的代码示例，该文件获得了“text/ html”内容类型。

以下是确切的（Groovy）代码：

class S3Test {
    static void main(String[] args) {

        def s3 = new AmazonS3Client()

        def random = new Random()
        def bucketName = "raniz-playground"
        def keyName = "content-type-test"

        byte[] contentAsBytes = new byte[1024]
        random.nextBytes(contentAsBytes)

        ByteArrayInputStream contentsAsStream = new ByteArrayInputStream(contentAsBytes);
        ObjectMetadata md = new ObjectMetadata();
        md.setContentLength(contentAsBytes.length);
        md.setContentType("text/html");
        s3.putObject(new PutObjectRequest(bucketName, keyName, contentsAsStream, md))

        def object = s3.getObject(bucketName, keyName)
        println(object.objectMetadata.contentType)
        object.close()
    }
}

程序打印

text/html

S3 元数据也是这样说的：

以下是通过网络发送的通信（由Apache HTTP Commons调试日志记录提供）：

>> PUT /content-type-test HTTP/1.1
>> Host: raniz-playground.s3.amazonaws.com
>> Authorization: AWS <nope>
>> User-Agent: aws-sdk-java/1.9.6 Linux/3.2.0-84-generic Java_HotSpot(TM)_64-Bit_Server_VM/25.45-b02/1.8.0_45
>> Date: Fri, 12 Jun 2015 02:11:16 GMT
>> Content-Type: text/html
>> Content-Length: 1024
>> Connection: Keep-Alive
>> Expect: 100-continue
<< HTTP/1.1 200 OK
<< x-amz-id-2: mOsmhYGkW+SxipF6S2+CnmiqOhwJ62WfWUkmZk4zU3rzkWCEH9P/bT1hUz27apmO
<< x-amz-request-id: 8706AE3BE8597644
<< Date: Fri, 12 Jun 2015 02:11:23 GMT
<< ETag: "6c53debeb28f1d12f7ad388b27c9036d"
<< Content-Length: 0
<< Server: AmazonS3

>> GET /content-type-test HTTP/1.1
>> Host: raniz-playground.s3.amazonaws.com
>> Authorization: AWS <nope>
>> User-Agent: aws-sdk-java/1.9.6 Linux/3.2.0-84-generic Java_HotSpot(TM)_64-Bit_Server_VM/25.45-b02/1.8.0_45
>> Date: Fri, 12 Jun 2015 02:11:23 GMT
>> Content-Type: application/x-www-form-urlencoded; charset=utf-8
>> Connection: Keep-Alive
<< HTTP/1.1 200 OK
<< x-amz-id-2: 9U1CQ8yIYBKYyadKi4syaAsr+7BV76Q+5UAGj2w1zDiPC2qZN0NzUCQNv6pWGu7n
<< x-amz-request-id: 6777433366DB6436
<< Date: Fri, 12 Jun 2015 02:11:24 GMT
<< Last-Modified: Fri, 12 Jun 2015 02:11:23 GMT
<< ETag: "6c53debeb28f1d12f7ad388b27c9036d"
<< Accept-Ranges: bytes
<< Content-Type: text/html
<< Content-Length: 1024
<< Server: AmazonS3

这也是查看源代码向我们展示的行为 - 如果您设置了内容类型，SDK不会覆盖它。

因为您必须在发送之前设置内容类型，请使用 putObject 方法;

        ObjectMetadata md = new ObjectMetadata();

        InputStream myInputStream = new ByteArrayInputStream(bFile); 
        md.setContentLength(bFile.length);
        md.setContentType("text/html");
        md.setContentEncoding("UTF-8");

        s3client.putObject(new PutObjectRequest(bucketName, keyName, myInputStream, md));

上传后，内容类型设置为“text/html”"

这是一个工作的虚拟代码，检查一下，我刚刚尝试过，它正在工作;

public class TestAWS {

    //TEST
    private static String bucketName = "whateverBucket";

    public static void main(String[] args) throws Exception {
        BasicAWSCredentials awsCreds = new BasicAWSCredentials("whatever", "whatever");

        AmazonS3 s3client = new AmazonS3Client(awsCreds);
        try
        {
            String uploadFileName = "D:\\try.txt";
            String keyName = "newFile.txt";

            System.out.println("Uploading a new object to S3 from a file\n");
            File file = new File(uploadFileName);

            //bFile will be the placeholder of file bytes
            byte[] bFile = new byte[(int) file.length()];
            FileInputStream fileInputStream=null;

            //convert file into array of bytes  
            fileInputStream = new FileInputStream(file);
            fileInputStream.read(bFile);
            fileInputStream.close();

            ObjectMetadata md = new ObjectMetadata();

            InputStream myInputStream = new ByteArrayInputStream(bFile); 
            md.setContentLength(bFile.length);
            md.setContentType("text/html");
            md.setContentEncoding("UTF-8");

            s3client.putObject(new PutObjectRequest(bucketName, keyName, myInputStream, md));
        } catch (AmazonServiceException ase)
        {
            System.out.println("Caught an AmazonServiceException, which "
                    + "means your request made it "
                    + "to Amazon S3, but was rejected with an error response"
                    + " for some reason.");
            System.out.println("Error Message:    " + ase.getMessage());
            System.out.println("HTTP Status Code: " + ase.getStatusCode());
            System.out.println("AWS Error Code:   " + ase.getErrorCode());
            System.out.println("Error Type:       " + ase.getErrorType());
            System.out.println("Request ID:       " + ase.getRequestId());
        } catch (AmazonClientException ace)
        {
            System.out.println("Caught an AmazonClientException, which "
                    + "means the client encountered "
                    + "an internal error while trying to "
                    + "communicate with S3, "
                    + "such as not being able to access the network.");
            System.out.println("Error Message: " + ace.getMessage());
        }

    }

}

希望它有所帮助。